i want to make an electronic mosquito repellent which works on the principle of producing high frequency sound waves which r not audible to human beings but are audible for mosquito. i want the circuit to be as simple as possible yet functional. i have come up with this ckt during web searching but m not sure it wil produce the required results or not. its using a loud speaker on the output when all other ckts i found included either peizo tweeter or ultrasonic buzzer. can anyone take a look at the ckt n tell me if i should go implementing this ckt or not???


Circuit diagram and parts list:
Parts list:
R1: 220 ohms.
R2: 1 mega ohms preset.
R3: 5 kilo ohms variable resistor for volume control.
C1: 0.005 micro farad
C2: 1000 micro farad electrolytic
C3: 0.1 micro farad
IC1: IC 555 timer IC
S1: 8 ohms good quality speaker.
Circuit Diagram:
Click on the image to enlarge it:

 

What is the audio frequency you want to transmit? What are your sources?

Have you considered possible side-effects to nearby animals?

 

Mosquitoes don't have ears but I would imagine that they sense sound vibrations from the hairs on their antennae. The Dragon Fly is your friend and one of the very few predators of the Mosquito. Perhaps mimicking the sound vibrations of the Dragon Fly's wings may ward off the little blood sucking tormentors.

Chris

Edit: Personally, I like solutions that kill them!! The less humanely, the better!!

 

I built one of those for a friend of mine years ago. Don't know how effective it was on mosquitos as it drove his dog into howling fits everytime he turned it on.

 

Since you can't hear whether your circuit is working or not, it'll be handy for testing if you can detect the relevant frequency. The software oscilloscopes that use a computer's sound inputs might work (what frequency are you planning?), since they'll pick up to over 20kHz, well above human hearing.

 

An ultrasonic "mosquito repeller" DOES NOT WORK!

An ordinary 8 ohm speaker cannot produce ultrasonic frequencies. Some tweeters and piezo transducers can.

The 5k ohm volume control has a value that is much too high and is not needed anyway.

The 1000uF capacitor in series with the speaker is good down to 100Hz. It can be 4.7uF for 20kHz and higher ultrasonic frequencies. Its polarity is backwards.

You show a positive 5V and a negative 5V supply. Is the power supply a total of 10V or is it just a single +5V and 0V supply?

 

If mosquitoes are a problem at your location, I suggest you build a belfry and stock it with a small quantity of Purina Bat Chow.

 

If mosquitoes are a problem at your location, I suggest you build a belfry and stock it with a small quantity of Purina Bat Chow.

Never seen (smelled) that one but I suspect it has a strong smell when humid, isn't it?

 

Plant flowers.

Marigolds to be precise.

I have used them for years to repel mosquitoes.

Take your hand and pull a few leaves off of a plant and crush the leaves between your hands while rubbing them briskly back and forth. Then smear the leaves around your neck and upper back and along your arms.

The little insect devils don't like those aromatic chemical compounds that are produced by the marigold. Google will reveal more about the chemicals in them if you care to look for it.